Duct-type grain dryers (e.g., sometimes called mixed-flow grain dryers) typically do not have any screens that can plug or that may need to be cleaned. This can reduce the need for maintenance and may allow a wide variety of different grains to be dried.
In duct-type grain dryers, grain may flow downward under the influence of gravity, e.g., through a grain column containing a plurality of ducts. The grain may be dried by passing heated air through the grain as the grain flows downward through the grain column. In some duct-type grain dryers, some of the ducts in the grain column might direct the heated air into contact with the downward flowing grain. The heated air may then flow through the downward flowing grain and may be subsequently cooled by the grain. The cooled air may then be directed from the grain column by other ducts in the grain column.
In some applications, after heated drying, the grain might be cooled before the grain exits the grain dryer, e.g., to prevent deterioration during storage. Some duct-type grain dryers, for example, might use pressurized air cooling in their grain columns. For example, ducts might be used to direct the pressurized cooling air into the grain. However, pressurized cooling can result in undesirable heat loss and energy consumption.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternatives to existing cooling systems for duct-type grain dryers.